Field of the Invention
The inventions disclosed and taught herein relate generally to systems and methods for use in inspecting the stator section of motors and pumps having constructions similar to mud motors and Moyno-style pumps.
Description of the Related Art
Certain devices (e.g., certain motors and pumps) have lobed stators, the dimensions of which are important to the proper operation of the device, for example, downhole oilfield operations often utilize mud motors and municipal water systems often use Moyno-style pumps to transfer viscous materials. For purposes of the following discussion, a mud motor is described as one such exemplary device although it should be understood that the described subject matter is applicable to other devices.
At a high level, a mud motor is a form of a positive displacement pump that includes an elongated rotor section and an elongated stator section. The rotor section is typically formed of a hardened material, such as steel, and has an outer profile that defines one or more helically shaped lobes. The stator section typically defines a central bore and has a generally spiral fluted interior that defines a number of lobes, where the number of lobes defined by the stator interior is different from—and typically greater than—the number of lobes defined by the rotor exterior. The interior of the stator bore is commonly formed from, or lined with an elastic, deformable material, such as rubber.
A representative section of an exemplary mud motor, taken from prior art Patent Application Publication, US 2011/0116959, is illustrated in FIG. 1 (Prior Art). In the illustrated figure, the mud motor rotor is reflected by element 302 and the mud motor stator is reflected by element 308. As illustrated, the interior of the stator bore 304 defines a number of different ridge-like elements that may define a number of maximum interior stator bore diameter “valleys” and a plurality of ridges defining a plurality of minimum interior stator bore diameter ridges. Because of the shape of the stator bore interior, one would encounter a number of both ridges and valleys if one were to traverse the stator bore along its elongated (i.e., longitudinal) axis. Thus, the shape of the interior bore is non-uniform and the exact diameter of the interior diameter of the stator bore may change as one moves along its elongated axis. For most mud motor stator bores, the interior stator bore diameter dimension may transition back and forth from a dimension corresponding generally to the maximum interior diameter to one corresponding generally to the minimum interior dimension as one moves from one end of the stator bore to the other along its elongated axis.
In operation, a pressurized fluid (which may take the form of drilling fluid, drilling mud, compressed air or other gas, or any other suitable fluid) is forced through the space between the rotor and the stator and produces a torque that causes the rotor to rotate. The rotating rotor is commonly coupled to a drill bit through a drive shaft to facilitate a drilling operation.
A proper fit between the rotor and the stator of a mud motor is important to proper operation of the motor. To ensure a proper fit, it is often helpful to have accurate measurement data associated with the minimum diameters of the stator bore. Knowing these dimensions can allow one to select a properly sized rotor for a given stator and/or determine that the rubber interior of a previously used stator needs to be reworked or replaced. Moreover, knowing these dimensions can potentially allow one to determine the wear levels of a stator and/or whether different regions of the stator interior are wearing at different levels than other regions. Stator bore gages are sometimes used to obtain information about the interior diameters of mud motor stators.
Known stator bore gages, such as the SBG-5000 Stator Gage offered by Gagemaker, typically use a broad base, relatively elongated gage head with a floating element shoe to measure the minimum internal diameter of a mud motor stator at various discrete locations. The elongated gage head typically spans a plurality of stator bore ridges. In such gages, the gage is typically preset or calibrated using a round setting standard and then inserted into the interior bore of the stator to be inspected. The gage is then placed at predetermined location intervals, and at each of the predetermined locations, the operator actuates a lever to take a dimensional reading either from an analog indicator or from a digital readout box. The dimensional measurements can then be analyzed to provide information about the minimum stator bore diameter. Flat, elongated stator bore gage extension shoes can be used with such devices to allow use of the gage in stators of varying sizes. In some instances, the gage can include an electronic measuring device and a wired connection for providing the measurement data to a computing device (such as a laptop computer) for display and processing.
A representative example of a prior art stator bore gage 200 as described is illustrated in FIG. 2. As reflected in the figure a broad-based head 202 having a broad, elongated floating measurement shoe is coupled by an elongated (commonly stainless steel or carbon fiber) ridged shaft 204 to a handle element 206 having a movable lever. The handle element 206 is coupled by a connection cable 208 to a computing device (such as a portable desktop or laptop computer) 210 that receives power via a standard power cord 212. An elongated flat shoe 214 may be used for stator bores of a large diameter. In use, the stator bore gage 200 is inserted into a stator bore and the operator moves the head 202 to a first location and activates the lever on the handle element 206 to take a first reading. The operator then moves the head 202 to a different point and takes a second reading. This procedure may be repeated a number of times to take discrete measurements at specific locations.
While known gages, such as the one described in connection with FIG. 2, are capable of providing accurate information concerning the internal dimensions of a mud motor stator bore, time is required for the taking of the various discrete measurements and the accuracy of the measurements can vary depending on where the discrete measurements are taken and the hand position of the user at the time the measurements are taken. Moreover, because the head 202 spans several stator bore ridges, individual measurements of the various minimum diameters within the stator bore are not obtained.